The invention relates generally to devices for measuring sound pressure levels and more specifically concerns devices for measuring small differences between relatively high sound pressure levels at two different microphone sites.
Previous methods and devices for measuring the difference between two sound pressure levels include the gradient microphone and the measurement of absolute sound pressure levels over independent acoustical channels.
A gradient microphone measures the difference between instantaneous sound pressures over a distance much less than an acoustical wavelength. It has the disadvantage that it will not measure the difference between peak sound pressures over a distance comparable to or greater than an acoustical wavelength. The disadvantage of measuring the absolute sound pressure levels over independent acoustical channels is that conventional microphone systems are not sufficiently stable to resolve small differences in sound pressure levels.
It is therefore a primary object of this invention to provide a device for measuring small differences between relatively high sound pressure levels at two different microphone sites with greater precision than has been done in the past. Another object of this invention is to provide a device for measuring the difference between peak sound pressures over a distance comparable to or greater than an acoustical wavelength.
A further object of this invention is to provide means for compensating against changes in the sensitivity of one acoustical channel relative to another acoustical channel.
Other objects and advantages of this invention will become apparent in the following specification and drawings.